The present invention relates to an electrical machine.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
International publication WO 2008/098867 A1 discloses an electrical machine in the form of a so-called disk segment motor. The functional principle of a disk segment motors is that of linear motors, in which coils on the stator side are attached to the machine in order to produce a magnetic field, and permanent magnets are distributed on a rotating disk, in order to produce an excitation field. The drive operates on the same principle as that of a linear motor, in which the drive path is in the form of a circle, following the circumference of the rotating disk. Disk segment motors of this type have been used to produce very high torques. However, their design is not trivial since very strong magnetic attraction forces act between the stator-side laminated core and the permanent magnets on the rotor side. These become greater the smaller the air gap between the stator and rotor is chosen to be. However, in order to achieve a high machine efficiency, the air gap should be chosen to be as small as possible. To cope with the resultant strong axially acting attraction forces, the electrical machine should be made very stiff. Furthermore, in order to maintain the air gap, manufacturing tolerances for the shaft bearings must be kept correspondingly tight. The greater the torque to be produced by the electrical machine, the greater the diameter of the rotor disk must be chosen to be. However, this means that the attraction forces between the stator and rotor produce large tilting torques, corresponding to their lever arm, and these are passed into the machine frame via the shaft bearing.
The invention is based on the object of simplifying the design of an electrical machine having an air-gap field which is predominantly in the direction of the shaft axis.
It would therefore be desirable and advantageous to provide an improved electrical machine which obviates prior art shortcomings and is simple in structure while being reliable in operation and which has an air-gap field which is predominantly in the direction of the shaft axis.